Plasminogen activators (PAs) are involved in normal physiological processes such as cell migration, fibrinolysis and tissue remodeling, and abnormal physiological processes such as thrombosis and malignant transformation. Two salient characteristics of malignant cells are their greater mobility compared to normal cells and their ability to invade tissues. Clearly these two processes involve proteolytic activity. Since most cells exhibit PA activity, the difference in PA activity between a normal and a malignant cell must be quantitative. The major difficulty in studying PA activity has been the lack of sensitive, quantitative assays. We propose to synthesize three new classes of organic compounds with which to assay quantitatively the PA activity of cells in culture, to purify PAs in a single step, and to assay quantitatively the PA activity of single cells. The assay for the PA activity of cells in culture will be developed to the point where the activity that is measured is characteristic of a cell type and predictive of that cell's utilization of its PA activity in vivo. Purified PAs will be characterized biochemically, the genes cloned, and the more efficient PAs synthesized for clinical use. The single cell assya for PA activity will be used to characterize the regulation of the enzyme in cells within a population of cells and will be adapted into a quick, sensitive, cheap, and quantitative carcinogen assay. More specific objectives involve determining the degree of correlation between increased levels of PA activity and metastatic ability, isolation of specific inhibitors of PAs, the role of plasmin in tissue remodeling, the induction of a PA by estrogen, and the function of a PA activity in E. coli outer membranes.